The High Court has set a date to hear Cardinal George Pell's appeal against his convictions for abusing two choirboys in 1996 while he was Catholic archbishop of Melbourne.

Pell, 78, was convicted on five charges — one count of sexual penetration of a child under the age of 16 and four counts of committing an indecent act with, or in the presence of a child.

In March last year he was sentenced to six years' jail, with a non-parole period of three years and eight months.

In August, two of three judges from Victoria's Court of Appeal turned down Pell's primary ground of appeal, that the jury's verdict was unreasonable.

The judges unanimously dismissed two other grounds of appeal which argued that there were errors in the way the trial was run.

The High Court case will be Pell's final chance to seek to have his convictions overturned.

His offending took place in the sacristy at St Patrick's Cathedral in Melbourne, in what the sentencing judge described as a "brazen and forcible sexual attack on the victims".

Pell was the archbishop of Melbourne in the 1990s and eventually rose to the powerful position of Prefect for the Secretariat for the Economy, a position which essentially made him the Vatican treasurer.

Brisbane, Australia (CNN)Cardinal George Pell has been freed from prison after Australia's High Court unanimously overturned his conviction on five counts of historical child sex abuse.

The momentous decision, handed down Tuesday by Chief Justice Susan Kiefel, ends a five-year legal battle that started when a man in his 30s approached police alleging Pell had abused him as a child in the mid-1990s.

At the time, Pell was Vatican Treasurer and the highest ranking Catholic official to ever be publicly accused of child sex offenses. Pell strenuously denied the charges, which he dismissed in a 2016 police interview as a "product of fantasy."